UBRARY 

8NIVERSITY  OF      SCIENCES 
CALIFORNIA     J  UBRAJ5Y 


Proceed  in' 


•'     THE 


POUUHKEEPS1E    SOCIETY    01 

Natural    Science, 


VCMU       L 


QE 

VS/2 


CES 
LIBRARY 


STUDIES 

UPON   THE 

INCLINATION   OF  THE   EARTH'S   Axis, 

BY  CHARLES  B.  WARRING. 


Read  before  the  Poughkeepsie  Society  of  Natural  Science, 
Nov.  29,  1876. 

From  the  most  remote  period  known  to  history  or  tradition, 
Summer  and  Winter,  Spring-time  and  Autumn  have  divided 
the  year  as  now.  During  all  the  centuries  since  their  cause,  the 
inclination  of  the  earth's  axis,  has  been  unchanged.  Its  great 
importance,  an  inability  to  account  for  it,  and  an  undue  esti- 
mate of  the  fixedness  of  axial  direction  have  induced  in 
many,  the  belief  that  it  is  due  to  a  direct  exertion  of  Divine 
power.  But  as  the  axes  of  all  the  planets  and  the  Sun  are 
inclined  at  various  angles,  often  not  of  the  least  advantage 
in  reference  to  seasons  j^as,  for  example,  in  the  Sun  and 
MoonJ it  seems  that  their  obliquity  must  be  due  to  some  force 
active  before  the  historical  or  traditional  period  began,  per- 
haps at  the  formation  of  the  system.  This  leads  to  an 
inquiry  into  the  mode  of  its  genesis,  and  the  world's  as  a 
part  of  it. 

The  theory  suggested  by  Kant,  and  more  fully  developed 
by  Laplace,  accounts,  on  well-known  mechanical  principles, 
for  so  many  of  the  phenomena  of  the  solar  system,  and  has, 
according  to  the  spectroscope,  so  good  a  basis  in  the  present 
existence  of  true  nebulae,  that  it  is  generally  admitted  to  be 
wonderfully  near  the  truth,  it  not  the  truth  itself.  The  re- 


luctance  of  some  to  heartily  accept  it,  arises  from  the  fact 
that  while  it  seems  to  account  for  so  many  phenomena,  it  not 
only  fails  to  do  so  upon  closer  examination  but  actually  ap- 
pears to  be  contradicted  by  them. 

For  example,  the  sun  and  all  the  planets,  on  this  theory, 
ought"  to  move  in  one  direction,  both  on  their  axes  and  in 
their  orbits;  and  so  they  do — pretty  nearly.  Yet,  when 
accuracy  of  statement  is  required,  we  are  told  that  they  all 
vary,  the  direction  of  no  two  being  exactly  the  same.  The 
axial  motion  of  the  earth,  for  example,  crosses  the  orbital  at 
an  angle  of  231° ;  and,  with  variations  in  the  angle  of 
crossing,  the  same  is  true  of  all.  The  orbits  ought  to  lie  in 
the  plane  of  the  solar  equator ;  but  they  do  not :  nor  do  any 
two  of  their  planes  coincide  with  each  other.  Not  one 
planet  has  its  axis  perpendicular  to  its  own  orbit ;  although, 
according  to  the  theory,  they  all  ought.  The  orbits,  more- 
over, ought  to  be  circular ;  bat  all  are  more  or  less  eccentric. 
All  the  satellites  ought  to  be  in  the  planes  of  the  equators  of 
their  primaries;  but  I  doubt  if  one  is  really  so,  while 
Saturn's  eighth  satellite  is  about  12°,  and  our  moon  nearly 
181°,  out  of  place.  To  crown  it  all,  the  moons  of  Uranus 
and  Neptune  actually  go  backward. 

If  Laplace's  theory  be  true  there  must  be  some  way  to  ac- 
count for  these  apparent  contradictious. 

My  attention  was  drawn  to  this  subject  nearly  two  years 
ago;  and  the  conclusions  at  which  I  arrived,  as  \sell  as  the 
reasons  on  which  they  are  founded,  I  embodied  in  my  "  Cos- 
mology," an  essay  which  forms  Part  III  of  The  Miracle  of 
To-Day. 

I  therein  showed  that  a  key  to  all  these  perplexing  pecul- 
iarities is  found  in  the  addition  to  the  Nebular  Hypothesis  of 
one  condition,  to  wit,  that  in  the  gas-like  mass  from  which 
the  solar  system  was  evolved  certain  elevations  or  upheavals 
occurred  from  time  to  time,  rising  and  subsiding  like  waves 
upon  a  sea. 

Such  movements  seem  to  be  normal  in  our  system.     They 


bave  been  noticed  in  that  semi-nebulous  planet  Saturn  by 
Schroster,  the  two  Bonds,  Herschel  and  others,  and  been 
found,  by  actual  measurement,  to  rise  more  than  1,000  miles. 
They  present  the  characteristic  form  of  our  earth's  circum- 
polar  upheavals,  for  they  are  not  abrupt,  but  rise  so  gently 
that  it  is  impossible  to  mark  their  precise  limits,  resembling 
the  tidal  wave  in  mid-ocean.  Similar  movements  are  more 
than  suspected  in  Jupiter.  The  spectroscope  reveals  them 
in  the  Sun  exhibiting,  however,  an  intensity  and  abruptness 
in  harmony  with  the  energetic  action  there  going  on.  Nor  is 
our  present  solid  earth  free  from  them.  They  are  seen  in 
the  slow  elevation  of  Sweden,  and  of  many  other  places.  In- 
deed, to  quote  the  enthusiastic  language  of  Darwin,  "  daily 
it  is  forced  home  upon  the  mind  of  the  Geologist,  that 
nothing,  not  even  the  wind  that  blows,  is  so  unstable  as  the 
crust  of  the  earth." 

Finding  then,  that  there  are  now  actually  in  existence 
masses  of  nebulous  substance,  such  as  the  theory  requires, 
which,  if  subject  to  the  laws  of  matter  and  affected  by  these 
upheavals,  would  evolve  a  system  like  our  own,  and  account 
for  all  its  apparent  anomalies  and  seeming  contradictions,  I 
see  no  escape  from  the  belief  that  the  Nebular  Hypothesis  is 
a  true  statement  of  its  mode  of  formation.  Other  evidence 
than  this,  it  is  in  the  nature  of  the  case  impossible  to  obtain. 
For  similar  reasons  astronomers  accept,  as  true,  the  existence 
of  a  central  force  holding  the  planets  in  their  places.  No 
one  has  seen  or  can  see  this  force,  although  everybody  be- 
lieves in  it,  because,  if  true,  it  accounts  for  the  facts  to 
which  it  is  applied. 

On  condition  then,  that  the  earth  and  moon  were  once  one 
mass  of  nebulous  matter,  subject  to  the  laws  of  motion,  I 
showed  that  the  axis  of  the  earth  at  the  time  of  separation 
from  the  moon  was  inclined  not  more  than  5  deg.  9  min.,  or, 
in  other  words  not  more  than  is  the  orbit  of  the  moon  now. 

But  my  studies  in  a  parallel,  but  entirely  independent  line 
of  thought,  rendered  me  doubtful  whether  the  earth's  axis 

PBOC.  I'O'K.  SOC.  NAT.  SCI. — VOL.  I. 


was  not  at  tLat  time  very  considerably  less  inclined  than  5 
cleg.  9  rnin.,  and  hence  I  was  led  to  reconsider  the  matter. 
This  brought  me  into  regions  hitherto  unexplored.  I  took 
for  guidance  tvro  principles ;  first,  the  past  and  present  uni- 
formity of  the  laws  of  motion,  and  second,  a  like  uniformity 
of  the  laws  of  organic  being;  in  other  words,  that  both 
classes  of  laws  have  operated,  since  they  came  from  the 
great  Lawgiver,  as  they  operate  to-day.  Hence,  relying 
upon  the  belief  that  the  earth  and  the  moon  are,  and  ever 
have  been  as  obedient  to  gravitation,  as  the  tiniest  dew-drop 
that  gathers  on  a  blade  of  grass,  and  that  the  genera  and 
species  now  living,  identical  with  the  ante-glacial  vegetation, 
are  no  more  and  no  less  subject  to  the  influence  of  light  than 
were  their  ancestors,  I  have  followed  the  clue  which  these 
have  given  me,  and  pursued  my  investigation,  undismayed 
by  the  greatness  of  the  results,  and  undisturbed  by  their 
novelty. 

The  object  of  this  paper  is  to  lay  these  results  before  you 
and  to  explain  the  manner  in  which  they  were  attained,  as 
well  as  to  present  some  'other  matters  intimately  connected 
with  the  same  subject. 

I  started  with  the  self  evident  proposition  that,  if  the 
earth  was  formed  from  nebulous  matter  in  obedience  to  the 
laws  of  motion  and  gravitation,  undisturbed  by  any  other 
force,  its  axis  must  necessarily  have  been  perpendicular  to 
the  plane  of  its  orbit. 

Here  we  are  met  on  the  threshold  of  our  inquiry  by  the 
question,  how  could  a  belt  become  a  spheroid?  Having 
answered  that,  we  next  shall  seek  to  show  how  the  axis, 
which  was  normally  perpendicular,  became  inclined.  In  the 
third  place,  we  shall  endeavor  to  discover  how  great  this  in- 
clination was,  up  to  the  moment  of  the  earth's  existence 
separate  from  the  moon.  If  I  mistake  not,  it  did  not  then 
exceed  1°  SO7 ;  and  this  brings  us  face  to  face  with  the  fourth 
inquiry,  When  did  the  increase  to  its  present  obliquity  occur  ? 
And,  lastly,  in  this  part  of  our  subject,  What  was  the  cause 
of  that  increase  2 


The  last  two  questions  lead  to  the  examination  of  the  geo- 
logical record.  We  shall  study  the  influence  of  light  upon 
plant-life  especially,  not  neglecting  its  effects  upon  aniinal- 
life,  and  from  these  endeavor  to  discover  the  actual  distribu 
tion  of  light  in  those  periods.  We  shall  also  inquire  into  the 
cause  of  the  Glacial  period,  and  shall  eximins  Mr.  C roll's 
theory  with  special  reference  to  the  crucial  test  which  he  lias 
proposed. 

To  complete  our  "  study,"  we  shall  then  seek  a  solution  of 
an  apparent  mechanical  difficulty,  and  lastly  set  forth  a  pos- 
sible explanation  of  the  circumpolar  upheavals. 

First,  then,  how  could  a  belt  become  a  spheroid  ? 

In  a  nebula  left  solely  to  the  influence  of  gravitation  and 
the  laws  of  motion,  the  ring  evolved  would  be  homogeneous 
and  of  uniform  section.  Consequently,  if  undisturbed  by 
any  external  force,  it  would  continue  in  that  condition  for- 
ever, and  it  would  move  in  the  same  direction  as  the  central 
mass  (which  we  will  style  the  helioid,)  about  their  common 
centre. 

The  distance  between  the  two,  at  first,  was  very  small, 
and  for  this  reason,  in  accordance  with  Kepler's  law,  their 
times  of  revolution,  or  their  angular  velocities,  must  have 
been  nearly  equal.  A  point,  therefore,  on  the  ring  opposite 
a  point  on  the  helioid,  would  remain  nearly  opposite  for  a 
very  long  time.  In  fact,  there  will  at  first  be  but  little  rela- 
tive change  of  position  for  many  complete  revolutions.  This 
js  a  matter  of  very  great  importance,  since  in  connection  with 
•fhe  temporary  character  of  the  upheavals,  it  completely 
^eliminates  that  compensation  which  would  otherwise  come 
from  the  points  being  half  the  time  on  one  side  of  the  center 
X)f  gravity,  and  half  on  opposite  sides,  such  a  change  of  po- 
sition being  the  marrow  of  Lagrange's  theorem  as  to  the 
stability  of  our  system. 

If  now.  in  this  early  stage,  an  upheaval  occurred  upon  the 
helioid  near  its  equator,  it  is  evident  that  it  would  exert 
,an  increased  mftucnce  upon  tlae  rjpg,  depending  upon  jty. 


mass  and  distance.  It  would  accelerate  the  atoms  bohind  it, 
and  retard  those  in  front.  Hence,  would  result  a  crowding 
together  of  the  atoms  of  the  ring,  thus  forming  an  enlargement, 
or  nucleus,  at  a  point  nearly  opposite  the  upheaval.  The 
atoms  behind  would  have  their  centrifugal  force  increased, 
while  those  in  front  would  have  theirs  diminished.  From  this 
would  arise  a  condition  shown  in  Fig.  1,  which  represents  an 
equatorial  section  of  the  system,  just  after  the  mass  M,  has 
been  upheaved  and  the  nucleus  N  begun  to  form. 

Fiff  1. 


A  nucleus  once  made,  its  own  attraction  would  continue 
to  draw  to  itself  the  ring-matter  with  ever  increasing  power 
until  the  whole  belt,  if  undisturbed,  flowed  into  it. 

Such  a  gathering  would  generate  a  rotation  in  the  same 
direction  as  the  helioid,  but  with  a  velocity  at  first  very 
small. 

Here  I  may  remark,  although  outside  of  the  question  be- 
fore us,  that  the  present  rate  of  axial  motion  of  any  planet, 
is  evidently  derived,  first,  from  the  mass  and  position  of  the 
upheaval,  since  these  determine  the  difference  of  motion  in 
the  two  portions  of  the  belt  ancl  consequently  the  initial 


rotation  ;  secondly,  from  the  mass  and  diameter  of  the  ring, 
for  the  one  is  the  measure  of  the  attractive  force,  and  the 
other  determines  the  falling  distance  of  the  atoms  and  hence, 
their  velocity.  The  diameter  of  the  ring  also  determines  the 
effect  of  the  attraction  of  the  upheaval  and  of  the  nucleus 
upon  the  centrifugal  force,  and  hence  the  distance  of  the 
points  of  impact  of  the  ring  atoms,  each  side  of  the  medial 
line.  Lastly,  after  the  ring  had  been  absorbed,  a  further  in- 
crease of  axial  velocity  \vas  produced  by  the  radial  contrac- 
tion of  the  embryo  plaaet,  continuing  indeed  to  the  present 
moment.  The  present  length  of  the  day  of  any  planet  is  a 
function  of  all  these  quantities,  less  the  force  lost  by  the 
conversion  of  energy  into  other  forms.  Kirkwood's  Analogy 
takes  notice  only  of  the  masses  and  distances  of  the  planeU 
themselves  and  therefore  can  give  only  approximate  results. 
This  is  an  inviting  field  into  which  1  must  wander  no  further 
to-night. 

We  have  seen  how  a  belt  could  become  a  spheroid,  but  we 
are  reminded  that  if  left  to  itself,  its  axis  would  be  perpen- 
dicular to  the  plane  of  its  orbit,  and  would  remain  so.  How 
could  it  first  become  inclined  ? 

As  the  ring-matter  was  pouring  into  the  nucleus  N,  Fig.  1, 
on  the  one  side,  and  being  gathered  up  on  the  other,  there 
were,  in  effect,  two  streams  moving  in  opposite  directions, 
and,  hence,  there  resulted  a  lateral  pressure  which  caused  it 
to  elongate  as  in  Fig.  2,  just  as  a  bar  of  iron  under  the 

Fig  2. 


blows  of  a  hammer,  elongates  in  the  direction  of  the  axis 
about  which  it  rotates,    Tbis  evidently  would  be-in,  a  Plate  of 


8 

unstable  equilibrium  and,  therefore,  if  while  the  process  was 
going  on,  an  upheaval  occurred  at  some  distance  above  the 
equator  of  the  helioid  as  at  M,  Fig.  3,  it  would  cause  the 

Fiff.  3. 


planet  to  become  inclined  in  the  direction  indicated  by  the 
dotted  line,  a  movement  which,  once  commenced,  would  be 
aided  by  the  attraction  of  the  central  body. 

A  succession  of  such  masses  as  M,  properly  placed  would 
tilt  the  spheroid  to  any  extent,  from  0'  to  180°.  If  this 
change  of  position  exceeded  90°,  the  direction  of  rotation 
would  be  reversed  and  then  would  result  a  retrograde  move- 
ment like  that  of  the  moons  of  Uranus,  as  shown  in  my 
Cosmology. 

We  can  thus  see  how,  on  known  mechanical  principles,  the 
nebulous  spheroid  from  which  the  earth  and  moon  were  long 
afterward  to  be  evolved,  could  obtain  a  greater  or  less  ob- 
liquity. 

As  soon,  however,  as  the  ring-matter  was  all  gathered  and 
the  lateral  pressure  in  consequence,  ended,  the  embryo  planet 
began  to  assume  an  oblate  form,  thus  generating  greater 
stability  or  in  other  words  a  stronger  power  of  resistance  to 
any  external  force  wliich  might  thereafter  tend  tQ  change  its 
8,xiaJ  direction. 


From  this  nebulous  body  a  belt  was  eventually  separated, 
which  of  necessity  lay  in  the  plane  of  the  equator  of  the  mass, 
and  from  it,  in  the  manner  already  considered,  the  moon  was, 
in  due  time,  evolved.  At  this  time  the  axes  of  the  earth  and 
moon,  if  left  to  themselves,  must  have  been  parallel,  and  the 
orbit  of  the  latter,  have  been  in  the  plane  ot  the  other's  equator. 
We  know  the  axes  now  are  not  parallel  and  the  moon's  orbit 
is  not  in  the  plane  of  the  earth's  equator.  Hence  we  are 
absolutely  certain  that  two  of  these  have  undergone  a  change 
of  position  since  that  time  of  avulsion.  The  moon's  axis  is 
nearest  the  normal  inclination,  hence,  a  priori,  it  is  most 
reasonable  to  believe  that  it  has  undergone  little  or  no  change 
in  that  respect.  If  this  be  so,  then  the  earth  at  that  time 
was  inclined  no  more  than  the  moon  is  now,  i.  e.  H°.  The 
same  doctrine  of  upheavals  will  readily  bring  us  through  all 
the  mechanical  difficulties  to  the  present  condition.  It'  there 
were  such  movements  in  the  moon,  they  would,  if  polar,  tilt 
the  moon  yet  further  from  the  perpendicular ;  hence  I  con- 
clude that  none  occurred.  But  if  polar  upheavals  of  suffi- 
cient size  occurred  upon  the  earth,  they  would  first  tilt 
the  moon's  orbit  further  from  its  position ;  and,  second,  by 
the  reaction  of  the  moon,  as  well  as  by  solar  attraction,  tilt 
the  world  to  an  extent  depending  upon  their  size  and 
duration.  The  world  is  tilted  22°  further  over,  and  the  orbit 
of  the  moon  has  moved  from  its  then  position  to  5°  9'.  In 
some  way  and  at  some  time  time  a  change  of  position  really 
occurred.  The  one  which  I  have  laid  before  you  seems  to  me 
the  easiest  and  most  natural  way.  The  change  could  not  occur 
without  outside  force  of  some  kind,  and  I  know  of  none  that 
"we  have  a  right  to  invoke  save  that,  whatever  it  is, 
which  has,  during  all  the  past  to  the  present  day,  manifested 
itself  in  immense  uplifts  either*  of  the  nebulous  matter  or  of 
the  solid  crust.  By  outside  force,  I  ought  perhaps  to  say, 
is  meant  some  other  force  than  the  attraction  of  gravitation 
and  the  laws  of  motion. 

I  conclude,  then,  as  at  least  the  most  probable  result,  that 


10 

when  the  lunar  belt  left  the  earth  the  axis  of  the  latter  was 
inclined  not  more  than  U°,  and  that  consequently  the  increase 
to  231°  occurred  at  some  subsequent  period. 

Our  next  inquiry  is,  Is  there  any  evidence  of  the  existence 
of  this  perpendicular  axis  ? 

I  remark,  first,  that  if  such  a  condition  continued  until  the 
earth  had  become  covered  with  plants  and  peopled  with  ani- 
mals, we  should  expect  indications  of  it  in  the  early  history 
of  our  globe.  We  know,  however,  that  if  it  did  so  continue, 
it  ceased  before  the  historic  period  commenced. 

A  careful  examination  of  all  possible  causes  of  such  a 
movement  as  increasing  the  obliquity  from  H°  to  23*°,  leads 
to  the  conclusion  that  no  physical  cause  would  be  adequate 
to  such  an  effect,  except  the  most  enormous  polar  upheavals 
— large  enough  to  make  our  globe  prolate.  Such  an  up- 
heaval would  engender  intense  cold.  Hence,  if  such  an 
event  occurred,  there  should  be  found  somewhere  between 
the  earlier  conditions  of  plant  and  animal  life,  and  the  historic 
period  a  time  of  world- wide  cold.  Conversely,  it*  on  exami- 
nation we  find  that,  in  the  earlier  periods,  conditions  did  actual- 
ly prevail  which  no  ingenuity  can  account  for  on  any  other  sup- 
position consistent  with  uniformity  in  the  action  of  the  laws 
of  life,  that  these  conditions  were  followed  by  polar  upheavals 
(of  whose  extent  we  know  comparatively  nothing)  accompa- 
nied by  great  cold,  and  if  we  find  too  that  the  orbit  of  the 
moon  has  moved  away  from  that  supposed  normal  position 
precisely  as  it  would  have  done  had  it  been  acted  upon  by 
the  attraction  of  such  upheavals,  then  I  submit  that  the  proof 
of  such  an  axial  change,  of  its  cause  and  epoch,  approaches 
demonstration. 

Before  examining  the  evidence,  I  would  call  attention  to 
the  fact  that  the  question  is  not  in  the  least  whether  the 
earth  has  ever  changed  the  direction  of  its  axis.  That  is  a 
conclusion  absolutely  involved  in  the  once  nebulous  condition 
of  our  Cosmos.  I  remark  also  that  it  is  not  a  change  in  the 
position  of  the  pole  on  the  earth's  surface  of  which  .1  am 


II 

speaking.  It  is  its  direction  in  space  with  which  I  am  concerned. 
And,  lastly,  the  mechanical  difficulties  are  not  lessened  by 
placing  this  change  in  the  remote  past,  nor  by  supposing  that 
it  occurred  while  our  globe  was  in  a  gaseous  condition.  It 
would  require  as  much  force  at  one  time  as  at  another,  and 
in  either  case  it  was,  humanly  speaking,  an  effort  of  infinite 
power ;  Cosmically  speaking,  it  was  the  merest  trifle. 

We  shall  now  turn  to  the  records  which  are  found  in  the 
rocks,  and  seek  to  discover  what  is  the  story  which  the 
fossils  tell. 

Looking  over  the  past,  we  are  first  struck  by  the  marvel- 
ous uniformity  of  plants  and  animals  in  all  latitudes.  "No 
marked  difference  between  the  life  of  the  Primordial  period 
in  warm  and  cold  latitudes  has  been  observed,"  (Dana's 
Manual,  p.  181.)  "Identical  species  are  found  in  the  strata 
near  Lake  Winnipeg  and  in  Alabama.  The  living  species  in 
the  waters  between  the  parallels  of  30°  and  45°  were  in  part 
the  same  with  those  that  flourished  between  65°  and  SO0/'  (p. 
253.)  When  we  come  down  to  the  Carboniferous  Age,  we  find 
according  to  Lesquereux  (Bulletin  of  U.  S.  Geol.  and  Geog- 
Survey,  1876,  p.  247,)  "a  uniformity  of  vegetation  over  the 
whole  northern  hemisphere,  if  not  over  the  whole  surface  of 
the  earth." 

Authorities  differ  as  to  the  degree  of  heat  indicated  by  the 
carboniferous  flora.  They  probably  did  not  require  a  torrid, 
but  a  decidedly  warm  climate.  It  is  not,  however,  the 
temperature  to  which  I  wish  to  direct  your  attention,  but  the 
fact  that  the  same  plants  and  animals  grew  in  all  latitudes, 
evidence  of  which  can  be  multiplied  to  an  indefinite  extent. 

As  to  the  identity,  or,  at  least,  intimate  relationship  of 
species  in  places  of  very  widely  different  latitudes,  I  find  Sir 
Charles  Lyell,  on  page  217  of  his  Principles  of  Geol.,  1873, 
saying :  "  The  same  genera,  and,  to  some  extent,  the  same 
species  of  ammonites,  and  some  other  shells,  occur  also  in 
formations  of  the  same  age  in  India.  In  a  northerly  di- 
rection the  same  formations  reach  within  13  2°  of  the  Dole." 


12 

*  *  *  #  *  *  "  Remains  of  a  large  Ichthyosaurus,  of 
Liassic  type,  were  brought  from  latitude  77°  16',  by  Sir  Ed- 
ward Belcher.  Others  were  found  in  Jurassic  strata,  in 
Spitzbergen,  in  latitude  78°  30V 

In  this  uniformity  of  animal,  and,  more  especially,  of  plant 
life,  there  will  be  found,  if  I  mistake  not,  indications  of  the 
highest  importance  as  to  the  position  of  the  earth's  axis,  i.  e., 
as  to  its  obliquity  to  the  ecliptic.  I  see  no  evidence  that 
latitudes  have  ever  changed. 

Next  to  food,  heat  and  light  are  essential  to  the  growth 
and  mature  development  of  organisms.  Scientists  in  refer- 
ence to  the  early  history  of  our  globe  have  confined  their  ef- 
forts to  accounting  for  the  uniformity  of  heat,  utterly  ignor- 
ing the  eifects  of  light.  Both  will  be  found  yielding  evi- 
dence as  to  the  question  which  I  am  endeavoring  to  solve,  but 
light  far  more  than  heat. 

The  earth  receives  from  the  sun  both  light  and  heat.  The 
latter  enters  our  atmosphere  freely,  but  cannot  as  easily  es- 
cape. Prof.  Tyndall,  by  a  series  of  beautiful  experiments 
upon  the  passage  of  heat  from  sources  of  low  temperature 
through  vapors  and  gases,  has  shown  that  even  a  small 
amount  of  watery  vapor  in  the  atmosphere  acts  like  a  thick 
blanket  to  keep  in  the  heat,  and  that  other  vapors  and  gases, 
as  carbonic  acid,  for  example,  behave  in  the  same  manner^ 
and  even  with  greater  intensity. 

These  important  discoveries  render  it  possible  to  see  how 
the  temperature  of  the  globe  might  vary  exceedingly  at 
different  epochs,  although  receiving  equal  amounts  of  heat 
from  the  Sun.  On  the  same  principle,  plants  under  glass  are 
kept  warmer  than  those  in  the  open  air.  The  glass,  like  the 
vapors,  lets  the  solar  heat  in,  but  does  not  permit  that  radi- 
ated from  the  plants  and  the  soil  in  which  they  stand,  to 
escape. 

It  is  well  known  that  the  arrangement  of  the  land,  either 
as  to  elevation  or  extent,  and  the  volume  and  direction  of 
ocean- currents,  exert  a  controlling  influence  on  the  tempera- 


13 

tare  of  localities ;  and,  hence,  this  does  not  afford  any  very 
certain  indication  of  the  amount  of  heat  received  from  the 
Sun. 

I  shall  say  nothing  of  internal  heat,  because,  although  the 
world  had  once  been  intensely  hot,  yet,  at  the  time  of 
the  coal  deposits,  and,  probably  long  before,  it  had  ceased 
to  radiate  any  appreciable  quantity. 

If  the  atmosphere  in  the  earlier  periods  was  freer  from  car- 
bonic acid  and  watery  vapor  than  DOW,  and  the  axis 
was  inclined,  as  at  the  present  day,  the  climate  of  the  arctic 
regions  must  have  been  much  colder,  and,  vice  versa,  if  these 
were  more  abundant,  the  temperature  must  have  been  warm- 
er ;  upon  the  whole,  therefore,  the  distribution  of  heat  is 
affected  so  greatly  by  influences  independent  of  the  earth's 
axial  position,  that  no  conclusion  of  value  can  be  drawn  from 
it  in  reference  to  the  obliquity. 

We  are  not,  however,  left  without  any  clue.  There  is  the 
other  force  of  which  I  have  spoken,  and  which,  thus  far,  in 
all  attemps  to  solve  this  problem,  has  been  ignored.  Its  im- 
portance to  plant  life  is  scarcely  second  to  that  of  heat,  since 
disease  and  death  in  nearly  all  cases,  inevitably  follow  the 
absence,  or  too  small  quantity  of  either. 

This  force  is  LIGHT. 

If  plants  are  kept  in  a  cold,  dry  place,  they  may  long  be 
unaifected  by  the  absence  of  light,  but  it  becomes  vitally 
important  if  they  are  surrounded  by  an  atmosphere  "  warm 
and  moist "  as  in  Miocene  and  pre-M  iocene  times.  Few  plants 
deprived  of  this  necessary  stimulus,  will  long  survive  in  such 
conditions,  as  every  gardener  can  bear  witness. 

Light  at  any  point  may  be  diminished  by  clouds,  or  mist, 
but  in  no  way,  increased.  The  total  annual  amount  falling 
upon  a  given  surface,  as  a  square  yard,  is  determined  solely 
by  the  latitude,  save  so  far  as  it  may  be  affected  by  clouds, 
and  consequently  it  is  independent  of  the  inclination  of  the 
earth's  axis.  But  the  distribution  of  that  light,  e.  g.,  whether 
it  be  concentrated  into  a  short  period  of  uninterupted  sun- 


14 

shine,  followed  by  a  total  absence  of  solar  rays  for  a  long  po- 
lar night,  depends  wholly  upon  the  inclination. 

Hence,  if  we  know  how  such  distributions  would  affect 
plant-life,  and  if  we  also  know  what  was  the  flora  of  those 
early  periods,  we  have  the  means  of  determining  whether  the 
earth's  axis  was  yet  in  the  position  which  it  had  wThen  the 
lunar  belt  was  avulsed,  or  whether  it  had  attained  its  present 
obliquity.  Most  plants  require  what  may  be  styled  a  speci- 
fic amount  of  light.  Few  do  well  in  the  shade.  From  the 
character  of  the  early  vegetation,  it  is  evident  that  the  climate 
was  "  warm,  moist  and  equable,"  (Dana,  Ly  ell,  &c.)  If  plants 
are  left  for  months  in  a  warm,  moist  and  dark  cellar, 
it  is  well  known  that  their  foliage  becomes  colorless  and  un- 
natural. I  have  never  heard  of  their  flowering,  and  it  seems 
impossible  that  they  could  mature  their  seed.  The  same 
plants  will  not  do  well  under  these  conditions  and  under  the 
direct  and  full  light  of  the  Sun.  If  the  axis,  in  the  Cretaceous 
for  example,  was  inclined  231°,  the  condition  as  to  light 
would  be,  say,  in  latitude  80°,  for  four  months  as  in  the  cel- 
lar, and  for  four  months  as  in  the  direct  sun-light.  If  they 
really  lived  and  did  well,  the  flora  must  have  been  peculiar 
to  those  latitudes.  But  we  find  all  along  down  to  the  Mio- 
cene certainly,  in  each  epoch,  a  wonderful  sameness  of  species 
all  over  the  world — the  same  trees  "  flourishing  luxuriantly  " 
from  Florida  to  Spitzbergen,  (latitude  79°)  and  beyond. 

In  Spitzbergen,  if  the  axis  was  then  inclined  as  now,  the 
night,  "  warm  and  moist,"  was  four  months  long.  It  is  incon- 
ceivable that  under  such  different  circumstances,  as  to  this 
powerful  element  in  plant  evolution,  no  new  types  were 
formed  fitted  to  these  extremes. 

It  is  said  that  Arctic  plants  are  found  on  the  tops  of  high 
mountains,  where,  although  they  have  Arctic  cold,  they  are 
also  exposed  to  days  and  nights  of  comparatively  equal  length, 
and  that  they  flourish  there  as  well  as  in  northern  latitudes 
with  their  long  winter  nights. 

Admitting  the  identity   of  the  species,  which  is  question- 


15 

able,0  still  the  cases  are  not  analogous.  The  Arctic  plants, 
accustomed  to  a  stagnation  of  six  to  nine  months'  duration, 
may  well  be  indifferent  as  to  where  that  time  is  spent, 
whether  in  the  cold  and  darkness  of  an  arctic  night,  or  the 
cold  and  light  of  a  lower  latitude.  But  the  plants  of  the 
Carboniferous  Age  were  not  polar  plants  at  all,  but  tropical, 
nor  were  they  accustomed  to  a  sleep  of  six  or  nine  months, 
nor  at  that  remote  period  was  there  any  Arctic  cold  to  pro- 
duce hibernation,  but  a  *  warm,  moist,  equable  atmosphere,1 
in  which  they  '  flourished  luxuriantly.' 

Mutatis  mutandis,  the  same  remarks  apply  to  the  lew 
plants  of  the  temperate  zone  that  have  straggled  to  the  far 
north  (Smith's  Sound),  \vhosc  dwarfed  and  scanty  growth  is 
in  in  marked  contrast  to  the  luxuriant  growth  of  the  coal- 
forming  period.  In  like  manner  stand  in  sharp  opposition 
the  vigorous  growth  on  Spitzbergen,  of  which  I  have  spoken, 
and  the  dwarfed  willows  that  are  to-day  their  successors. 

Moreover  if  then,  as  now,  there  were  long  days  and  nights 
varying  from  four  months  of  consecutive  sunlight,  to  as  many 
months  of  darkness,  it  is  utterly  impossible  that  there  could 
have  been  any  great  "  evenness  "  of  temperature.  For  al- 
though there  was  an  enormous  amount  of  carbonic  acid  in 
the  air,  its  only  effect  was  to  make  the  process  of  refrigeration 
in  the  long  nights  more  slow.  It  could  add  nothing  to  the 
heat.  The  temperature  would  still  be  dependent  upon  the 
sun  or  ocean  currents.  At  most,  the  latter  could  add  only  as 
much  heat  in  winter  as  in  summer  (they  would  really  add 
less)  ;  consequently  the  difference  which  wonld  arise  from  a 
steady  addition  of  solar  heat  for  four  months  and  a  total  ces- 
sation for  an  equal  time,  must  have  been  very  considerable. 
We  know  that  the  average  temperature  of  those  regions  at 
the  present  time  varies  between  the  coldest  and  the  warmest 
month  nearly  80°.  This  however  does  not  give  a  just  idea  of 

*  Darwin,  Origin  of  Species,  p.  338,  says,  "It  should,  however,  be  observed  that 
hese  plants  are  not  strictly  Arctic  forms ;  for,  as  Mr.  H.  C.  Watson  has  remarked, 
'in  receding  from  polar  towards  equatorial  latitudes,  the  Alpine  ov  Mountain 
floras  really  become  less  and  less  Arotio.'  " 


16 

the  true  difference,  for  the  thermometer  is  carefully  shielded 
from  the  direct  rays  of  the  sun  while  the  vegetation  has  no 
such  protection.  Hence  with  an  axis  inclined  as  now,  uni- 
formity of  temperature  was  impossible. 

But  if  tho  axis  was  then  nearly  perpendicular,  the  climate 
could  not  have  been  other  than  equable.  The  same  amount 
of  heat  being  received  each  day  from  the  sun  and,  the  same 
amount  being  each  night  radiated  into  space,  the  temperature 
must  have  been  uniform  all  the  year. 

Whether  the  result  was  a  warm  or  a  cold  climate,  it  con- 
tinued without  variation,  until  internal  forces  produced  either 
a  change  of  the  altitude  of  the  earth's  surface  or  of  its 
arrangement. 

That  the  result  of  such  days  and  nights  as  the  world  then 
had,  was  not  cold,  is  shown,  not  merely  by  the  flora  of  arctic 
lands,  but  by  the  corals  of  arctic  waters.  Indeed  these  are 
no  small  evidence  of  the  absence  of  long  nights  where  they 
lived.  It  is  well  known  that  they  die  below  a  certain  depth. 
Dana,  page  118,  Corals  and  Coral  Islands,  says, 

"  As  to  the  origin  of  this  small  range  in  depth — about  120 
feet — temperature  must  be  admitted  as  a  cause.  Yet  it  can 
hardly,  in  this  case,  be  the  only  cause.  The  range  of  tem- 
perature, 85°  to  74°,  gives  sufficient  heat  for  the  development 
of  the  greater  part  of  reef  species,  yet  the  temperature  at  the 
100  feet  plane,  in  the  Middle  Pacific,  is  mostly  above  74°." 

So  it  is  not  lack  of  warmth  that  kills  these  creatures,  nor 
is  it  any  impurity  in  the  wat?r,  for  certainly  the  impurities 
do  not  undergo  any  such  corresponding  increase  of  intensity. 
The  pressure  is  not  an  element  affecting  creatures  that  are 
composed  of  tissues  filled  with  water,  and  not  with  air.  The 
only  conceivable,  variable  element  capable  of  producing  any 
effect,  is  light.  The  fact  that  corals  flourished  is  strong  cor- 
roborative proof  that  the  polar  waters  were  not  deprived  of 
light  for  consecutive  months. 

Nor  is  it  an  objection  to  this  view  that  the  corals  are 
destitute  of  organs  of  sight,  for  in  no  case  is  the  health  or 


17 

vigor  affected  through  the  eyes  of  any  creature,  and  plants, 
whose  sensibility  is  marvelous,  are  as  destitute  of  such  or- 
gans as  the  Corals. 

It  is  very  true  that  there  was  during  the  Mesozoic  and  the 
Tertiary,  a  gradual  hardening  of  climate,  or  lowering  of  tem- 
perature, but  this  would  inevitably  occur  from  the  gradual 
loss  of  carbonic  acid  and  watery  vapor  and,  perhaps,  of 
other  impurities.  But  the  vegetation  of  these  northern  lands, 
all  along,  indicates  uniformity  of  light  and  not  extremes  of 
temperature. 

The  change  in  the  flora  of  those  regions  during  that  time 
was  what  was  to  have  been  expected,  if  the  days  and  nights 
remained  equal,  while  the  temperature  underwent  a  secular 
fall,  and  the  air  grew  drier  and  purer. 

In  view,  then,  of  the  records  of  Geology  I  think  I  am  justi- 
fied in  concluding  that  until  the  end  of  the  Tertiary 
there  were  no  such  long  nights  in  polar  regions,  as  there 
are  now.0 

It  may  be  said  that  the  amount  of  light  which  in  a  year 
falls  upon  a  square  foot  in  Florida  for  example,  is  four  times 
as  great  as  that  which  falls  upon  the  same  space  in  Spitz- 
bergen.  This  statement  is  equally  true  whether  the 
obliquity  of  the  axis  was  0°  or  23  i°  for  as  I  have  said,  the 
obliquity  does  not  effect  the  total  quantity  of  light.  In 
the  former  case,  it  would  be  uniformly  distributed,  equal  days 
following  equal  nights,  while  in  the  latter,  there  would  be 
the  greatest  possible  variation,  and  this,  continued  for  cen- 
turies, would  prevent  that  uniformity  of  vegetable  and  animal 
life  which  is  known  to  have  prevailed  in  the  Miocene  and 
before,  in  all  latitudes. 

It  appears  to  me  quite  doubtful  whether  the  polar  plants 
of  that  period  could  have  continued  their  kind  at  all,  if  they 
had  to  pass  four  months  in  darkness  in  a  "  warm  and  moist  " 
place.  The  fact  of  their  continued  existence  is  strong  proof 
that  no  such  nights  prevailed. 

*I  have  discussed  this  which  tray  Ire  styled  the  biological  rart  of  the 
question,  at  greater  length  in  my  *•  Cosmology,"  in  reference  to  the  effects  of  light 
upon  plants  and  animals. 


18 

Ft  may  be  said  that  in  any  case  there  must  have  been  a: 
great  inequality  between  the  polar  and  the  equatorial 
amount  of  heat  received  from  the  sun. 

To  this  I  would  reply  :  If  the  air  was  rich  in  carbonic 
acid,  and  if  the  path  of  the  sun  from  tropic  to  tropic 
was  almost  nil.,  there  would  result  an  equatorial  belt 
of  clouds  shielding  those  regions  from  a  heat  that  otherwise 
might  destroy  all  life. 

There  are,  at  the  present  day,  two  quite  uniform  belts  of 
clouds,  one  north  and  the  other  south  of  the  equator.  In 
the  conditions  I  have  supposed  these  belts  would  probably 
touch  each  other,  and  the  light  which  passed  through  might 
well  be  no  greater  than  that  which  fell  upon  circumpolar  re- 
gions. 

This  cloud  covering  reaching  from  the  equator  to  a  con- 
sideiable  distance  north  and  south,  would  give  the  condi- 
tions which  the  coal  flora  demanded,  warmth,  moisture,  and  a 
moderate  degree  of  light.  Ferns  of  the  tropics  are  most  lux- 
uriant in  moist  woods.  Equiseta  and  Lycopods,  as  well  as 
ferns,  like  shady  and  moist  places.  (Dana,  Manual,  p.  354). 
If  the  cloud  covering  stopped  a  considerable  distance  short 
of  the  poles,  perhaps  in  latitude  50°  or  60°,  above  that  the 
diminished  altitude  of  the  sun  would  deprive  it  of  the  inten- 
sity which  would  have  rendered  it  fatal  in  the  tropics,  and 
hence  the  coal  flora  was  able  to  flourish  there  also. 

That  which  the  clouds  did  for  the  light,  ocean  cui rents  did 
for  the  tropical  heat ;  they  equalized  it  by  carrying  it  from 
equatorial  to  high  latitude  regions.  These  currents  being, 
in  the  absence  of  changing  seasons,  absolutely  uniform,  and 
the  sun  giving  each  day  in  the  year  the  same  amount 
of  heat,  the  temperature  of  the  polar  regions  must  have  been 
as  invariable  as  that  at  the  equator. 

In  view,  therefore,  of  the  evidence  which  geology  gives  as  to 
the  uniform  distribution  of  LIGHT,  evidence  corroborated  by 
the  uniformity  of  temperature  in  high  or  low  latitude,  it  is 
difficult  to  avoid  the  belief  that  the  axis  of  our  planet  re- 


tained  its  original  inclination  of  1=>  30',  well  into  the  Plich 
cene. 

The  mild  climate  of  the  Tertiary  was  followed  by  intense 
cold.  Gradually  the  previous  plants  and  animals  disappeared 
and  an  almost  earth-wide  winter  set  in.  How  long  it  con. 
tinued  there  are  no  means  of  knowing,  but  at  last  it  drew  to 
an  end,  and  warmth  returned  to  regions  long  buried  in  snow 
and  ice.  Once  more  the  world  was  clothed  in  verdure  ancl 
adorned  with  forests.  The  air,  the  land  and  the  water 
again  abounded  with  life.  As  soon  as  the  records  become 
sufficiently  distinct  to  be  read,  there  is  no  longer  one  type  of 
vegetation  found  from  Florida  to  Spitzbergen.  Some  species 
once  inhabiting  the  latter  country  are  yet  seen  in  sub-tropical 
regions,  but  in  the  circumpolar  lands  are  found  an  artic  flora 
and  fauna  adapted  to  extremes  of  heat  and  cold  as  well  as 
to  long  alternations  of  light  and  darkness.  . 

These  alternations  are  due  to  the  present  large  inclination 
of  the  earth's  axis.  There  seem  to  have  been  none  before  the 
Glacial  Period  ;  they  occur  now,  hence  I  conclude  that  during 
the  interval  was  added  the  needed  increase  of  22°,  to  which 
we  owe  the  charming  variety  of  seasons. 

Was  there  any  connection  between  this  movement  of  the 
axis  and  the  cold  ?  Much,  I  think,  as  mutual  cause  and 
effect,  as  I  shall  now  seek  to  show. 

In  order  to  enable  the  lunar  and  solar  attraction  to  affect 
the  position  of  the  earth's  axis,  the  earth  needed  to  become 
prolate,  and  this  means  that,  if  the  equatorial  diameter  re- 
mained unchanged,  the  polar  regions  were  elevated  13 i 
miles,  or  if  the  equatorial  diameter  was  so  lessened  that  the 
volume  of  the  earth  was  unchanged,  the  poles  were  elevated 
8,  8  miles.  In  which  of  these  modes  the  elevation  really  oc- 
curred can  be  as  yet  only  a  matter  of  conjecture.  My  first 
impressions  which  I  stated  with  the  reasons  in  my  Cosmology, 
were  that  the  latter  was  the  true  mode,  but  further  reflection 
has  inclined  me  to  the  former,  as  involving  less  mechanical 
difficulties  and  as  being  possibly  explicable  by  the  theory  as 

PROG.  ro'K.  SOC.  NAT.  SCI. — VOL.  I. 


20 

to  its  cause  which  I  shall   in  the  course  of  the  evening  lay 
before  you. 

It  may  be  said  that  such  a  height  would  produce  a  press- 
ure sufficient  to  crush  the  hardest  granite,  and  that  is  true, 
but  the  granite  would  not  be  affected  for  the  same  reason 
that  it  is  not  now,  at  the  same  and  greater  depths  beneath 
the  surface.  It  is  compressed  and  held  in  place  by  the  later- 
al pressure.  A  polar  upheaval  of  this  character  and  extent 
would  readily  account  for  the  cold  of  the  early  Post-Tertiary. 
Conversely,  the  cold  thus  produced  would  aid  in  increasing  the 
required  prolateness  by  heaping  up  at  the  poles  the  oceans  as 
ice-caps.  Their  own  weight  even  on  so  moderate  a  slope 
would  press  the  ice  toward  the  equator,  and  give  the  motion 
needed  to  produce  the  scratches  and  other  traces  of  glacial 
action. 


The  existence  of  a  cold  period  following  the  Tertiary  will 
be  denied  by  few.  Traces  of  glacial  action  are  world-wide, 
reaching  from  polar  regions  to  well  towards  the  equator.  It 
is  also  generally  admitted  that  during  the  period  of  cold 
great  circum-polar  upheavals  occurred,  although  they  do  not, 
and,  in  the  nature  of  the  case,  cannot  give  such  evidence  as 
is  found  in  reference  to  depressions.  For  these  becoming 
covered  with  water,  received  in  the  soft  mud  and  preserved 
in  the  future  rocks,  the  remains  of  water  and  other  animals 
of  species  then  living,  thus  not  only  proving  the  downward 
movement,  but  even  establishing  its  chronological  position. 
Such  records  would,  of  necessity,  be  absent  from  elevations. 

An  important  proof  of  the  reality  of  such  an  upward 
movement  is  found  in  the  existence  of  fiords  in  high  latitudes, 
as  in  Norway,  Greenland,  Labrador,  Alaska,  Patagonia  and 
Chili.  These  are  long,  deep  bays  running  far  inland,  which, 
evidently,  have  been  eroded  by  water  and  ice.  Such  action 
could  occur  only  when  the  land  was  so  much  higher  than  now 
that  running  water  or  ico  could  erode  their  bottoms. 

The  only  real  question  Ls  as  to  the  magnitude  of  these 
movements,  and  of  that  we  are  utterly  ignorant,  and  certain- 


21 

ly  our  ignorance  is  no  answer  to  reasoning  based  on  facts~ 
which  we  do  know. 

The  cold  period  has  excited  great  inquiry  among  scientists, 
and  they  have  diligently  sought  its  cause.  Various  theories 
have  been  proposed  to  account  for  it.  One  of  these,  viz., 
circ  urn-polar  upheavals,  we  have  already  considered.  Anoth- 
er which,  perhaps,  should  rather  be  called  a  suggestion,  is 
advanced  by  Prof.  Langley,  in  Dec.  number,  1875,  of  Am. 
Journ.  Science  and  Art.  Referring  to  the  existence  of  an\ 
atmosphere  about  the  sun  which  absorbs  a  large  portion  ot 
the  heat  from  the  thermosphere,  and  which  is  liable  to  change 
of  constitution  from  the  varying  quantity  of  gaseous  matter 
ejected  into  it,  he  calls  attention  to  the  probability  of  the 
transmitted  heat  having  been  much  greater  in  amount  in 
the  remote  Geological  periods  than  now.  Audi  hence  there 
might  be,  and,  indeed,  would  be,  a  great  variation  in  thes; 
amount  of  heat  received  by  the  earth.  A  difference  of  2£L 
per  cent,  in  transmissive  power  would,  he  says,  probably 
raise  or  lower  the  temperature  100°  F.  from  the  present 
condition. 

Iii  this,  as  in  all  other  theories,  there  is  a  lack  of  explana- 
tion of  the  equability  of  temperature,  and  a  total  ignoring 
of  the  equability  of  light  distribution,  indicated  by  uniform- 
ity of  plant  life,  which  is  so  incomprehensible  in  connection 
with  the  long  polar  nights  and  days  which  must  have  existed 
at  that  time  if,  as  scientists  suppose,  the  axis  was  inclined 
231°.  Hence  if,  in  some  way,  the  change  from  warm  to  cold 
and  from  cold  to  present  warmth,  could  be  accounted  for, 
the  problem  would  be  but  half  solved. 

Mr.  Croll  has  proposed  another  theory  which  I  shall  discuss 
somewhat  at  length,  as  it  now  occupies  a  very  prominent 
position,  and  has  been- accepted  by  many  scientists  as  offer- 
ing a  true  explanation  of  the  cold  of  the  Glacial  Period,  and 
as  it  has  more  or  less  bearing  upon  the  extent  and  epoch  of 
the  primordial  inclination  of  the  earth's  axis. 

In  hia  "  Climate  and  Time,"  Mr,  Croll  endeavors  to  show 


22 

that  the  cold  of  the  glacial  epoch,  was  not  due  to  changes 
in  the  elevation  of  the  land,  but,  indirectly,  to  variations  in 
the  eccentricity  of  the  earth's  orbit  and  in  its  obliquity,  com- 
bined with  the  precession  of  the  equinoxes.  I  say  "indi- 
rectly," because  he  admits  that  no  increase  of  heat  or  cold 
could  come  from  astronomical  conditions  alone.  Indeed,  he 
styles  'the  assertion  "  absurd."  This  certainly  differs  very 
widely  from  the  view  generally  taken  of  his  theory,  and  it 
enables  him  to  avoid  the  force  of  most  of  the  arguments  thus 
far  brought  against  it. 

It  is  to  be  observed  that  he  too  ignores  the  uniform  distri- 
bution of  light,  as  well  as  the  difficulty  of  keeping  uniformi- 
ty of  temperature,  in  latitudes  where  four  months  of  uninter- 
rupted sunshine  were  followed  by  darkness  of  equal  du- 
ration. 

The  question  of  a  possible  change  in  the  direction  of  the 
earth's  axis  is  not  considered  by  him  any  farther  than  to 
state  that  "  it  has  been  shown  by  Professor  Airy,  Sir  Wm. 
Thomson,  and  others,  that  the  earth's  equatorial  protuber- 
ance is  so  great  that  no  geological  change  on  its  surface 
could  ever  possibly  alter  the  position  ot  the  axis  of  rotation 
to  an  extent  that  could  at  all  sensibly  affect  climate." 

But  if  the  earth,  from  any  cause,  became  temporarily  a 
true  sphere,  and  then  the  contents  of  the  oceans  were  piled 
as  ice  about  the  poles,  the  case  would  be  very  different. 
The  latitudes  indeed  would  not  vary,  but  the  direction  of 
the  axis  in  space  would  undergo  a  change  due  to  the  at- 
traction of  the  moon  and  sun.* 

Mr.  CrolFs  theory  assumes,  without  inquiry  the  present 
axial  inclination  to  have  been  attained  before  the  geological 


*  The  possibility  of  such  a  polar  upheaval  as  appears  to  me  to  have  occurred 
seems  never  to  have  been  considered.  Newton  touches  upon  it  in  the  "  Prin- 
cipia"  so  far  as  to  assert  that  if  the  earth  were  a  sphere,  and  a  mass  were  laid 
upon  it  at  either  pole,  it  would  produce  a  recession  df  the  equinoxes;— and 
tbat  implies  the  movement  of  the  axis  towards  the  ecliptic  in  ever-widening 
spiral  until  equilibrium  was  restored. 

The  effect  of  centrifugal  forces  generated  by  masses  placed  between  the 
poles  and  the  equator  is  curious,  and  is  related  in  a  very  interesting1  manner 
to  the  present  distribution  of  land  and  water;  I  have  discussed  the  prince 
pies  in  my  Cosm*»>ogry,^-J^iraf7es  of  To-Pay,  page  218. 


23 

record  begins.  It  also  requires  not  one  glacial  period,  but 
many. 

So  important  does  he  deem  this  last  that  he  styles  it  "  the 
grand  crucial  test  of  the  truth  of  his  theory,"  (p.  237.) 

This  has  induced  a  careful  study  of  the  formations  older 
than  the  Post-Tertiary  which,  in  his  opinion,  establishes  the 
existence  of  glacial  action  even  before  the  carboniferous  age. 
The  proof,  as  stated  by  him,  consists  in  the  existence  of  con- 
glomerates, having  the  appearance  of  glacial  debris,  but  in 
nearly  all  cases  destitute  of  the  characteristic  scratches.  Ad- 
mitting, however,  that  these  formations  are  due  to  ice-action, 
I  notice  two  circumstances  that  have,  as  it  seems  to  me,  a 
most  important  bearing  upon  their  proper  explanation.  The 
first  is  the  scant  and  limited  nature  of  these  remains.  There 
is  nothing  whatever,  approximating  to  the  world-wide  traces 
of  that  ice-period  which  followed  the  Tertiary.  Beds  of  con- 
glomerate of  those  older  periods  have  been  found  in  Scot- 
land, together  with  some  quite  large  boulders,  some  near 
Lake  Superior,  some  in  Nova  Scotia,  a  few  in  Ohio  in  a 
seam  of  coal,0  some  in  Australia,  which  Mr.  Selwyn  was  in- 
clined to  think  were  probably  of  glacial  origin.  Mr.  Bland- 
ford  thinks  he  found  evidence  of  ice  action  in  India.  Prof. 
Ramsay  has  suggested  that  similar  accumulations  in  Ger- 
many, betray  like  traces  of  old  ice  action.  There  are  some 
in  England,  and  some  in  Switzerland.  But  these  are  mere 
spots  compared  with  the  wide  spread  traces  left  by  the  great 
Glaciers  that  followed  the  Tertiary.  Their  remains  cover 
more  than  half  the  land  of  the  globe,  reaching  from  the  poles 
to  latitude  35  deg.  or  lower. 

M.  Geikie,  in  his  "Great  Ice  Age,"  supports  Mr.  CrolPs 
theory,  and  from  his  appendix  I  have  taken  the  substance  of 
the  last  paragraph  as  to  the  evidence  of  early  glacial  action.. 

The  second  important  circumstance  is  the  kind  and  distri- 
bution df  plant  lifej  which  seems  to  me  utterly  inconsistent 

*  These  may  have  been  dropped  from  the  rootSdf  floating  trees,  as  are  the  masses 
of  basaltic  rocks  oscasionnlly  found,  upon  the  coral  atolls  0f  the  Pacifio. 
Mnti.»  p,  3170 


with  this  theory.  That  I  may  do  no  injustice  I  quote  from 
Mr.  Geikie: 

"Now  if  we  were  to  judge  only  from  their  organic  con- 
tents, we  should  be  forced  to  admit  that  none  of  these  for- 
mations down  to  the  Miocene,  afford  any  trace .  whatever  of 
cold  or  glacial  conditions.  So  likewise  the  appearance  of  ice- 
transported  blocks  in  the  Miocene,  is  a  sore  puzzle.  The 
fossils  of  this  formation  speak  to  us  of  tropical  and  sub- 
tropical climates  having  prevailed  in  Central  Europe.  Nay 
more,  Miocene  deposits  have  been  detected  in  high  arctic 
latitudes.  Species  of  Sequoia,  Conifer®,  Poplar,  Willow,  Oak, 
Walnut,  Plum,  Andromeda,  Daphnogene,  and  several  other 
evergreens  grew  during  Miocene  times  in  North  Greenland ! 
Even  in  Spitzbergen,  abundant  traces  of  the  same  kind  of 
vegetation  have  been  preserved." 

Here  we  have  glacial  deposits  and  tropical  vegetation,  the 
glacial  deposits  "in  Italy,"  and  the  tropical  vegetation  in 
Spitzbergen !  Mr.  Geikie  gives  a  yet  more  remarkable 
instance  from  Prof.  Dawson,  who  describes  "  a  gigantic  esker, 
on  which  were  deposited  large  travelled  bowlders."  This 
was  found  on  one  side  of  a  coal  region,  where  the  character- 
istic plants  of  that  formation  were  growing. 

Well  does  Mr.  Geikie,  with  his  view  of  the  causes  of  the 
cold  epochs,  say  that  "  Geologists  are  puzzled  over  these 
facts !  "  Mr.  Croll  gets  along  with  them  by  the  assumption 
that  several  glacial  periods  occurred  in  alternation  with 
warm  ones  during  the  progress  of  the  same  formation.  That, 
for  example,  during  the  coal  age,  there  were  10,000  years  of 
warm  climate,  during  which  a  seam  of  coal  was  deposited ; 
that  this  was  followed  by  10,000  years  of  cold,  and  then 
10,000  years  more  of  warmth,  and  another  seam ;  and  thus 
for  an  unknown  number  of  alternations : — and  so  during  the 
other  Ages 

These  changes  from  hot  to  cold  and  from  cold  to  hot,  how- 
ever, admitting  their  occurrence,  being  dependent  upon  astro- 
nomical causey  could  not  have  been  sharp,  but  the  maxi- 


inum  heat  must  liavo  grown  less  very  slowly,  and  there  must 
have  been  an  intermediate  condition  of  long  duration  gradu- 
ally hardening  into  the  cold  or  glacial ;  and  there  is,  as  far 
as  I  see,  no  reason  to  doubt  the  tolerably  equal  duration  of 
each  of  these  periods.  In  a  cycle  of  22,000  years  there  must 
have  been  one  warm  period,  one  temperate,  one  cold,  and  a 
second  temperate,  each  continuing  about  5,500  years. 

If  there  were  no  animals  fitted  to  live  in  any  epoch  but 
the  warmest,  there  was  exhibited  the  remarkable,  and  I  may 
say,  inconceivable  spectacle  of  a  region  covering  more  than 
one-half  of  the  entire  land  surface  which  was  destitute  of  or- 
ganic life  for  nearly  three-quarters  of  each  great  cycle  of 
22,000  years,  a  region  too  which,  in  the  remaining  quarter, 
abounded  in  life,  and  which,  at  the  present  day,  has  an  ap- 
propriate flora  and  fauna;  the  latter  surpassing  that  of 
any  other  portion  of  the  globe  in  the  multitude  of  individu- 
als which  compose  it. 

If,  on  the  other  hand,  there  were  at  that  time  animals  and 
plants  fitted  for  a  rigorous  climate,  they  must  have  perished 
when  the  heat  of  Florida  reached  Spitzbergen,  and  probably 
as  far  beyond  as  land  extended  towards  the  pole. 

But  granting  that,  by  some  happy  although  inexplicable 
circumstance,  they  lived  through  the,  to  them,  fiery  heat  of 
the  cosmic  summer,  when,  in  the  cycle  of  time,  the  cosmic 
winter  came  on,  and  snow  and  ice  formed  a  covering  too  deep 
to  permit  the  land  animals  to  reach  the  scanty  vegetation  or 
to  supply  their  needs  from  the  seas,  they  must  have  perished 
where  they  were,  or  have  migrated  to  more  genial  climes. 
As  the  snow  gradually  edged  its  way  down,  many  gener- 
ations lived  and  died  in  each  successive  belt.  They  must 
have  spent  centuries  in  each  new  locality ;  and  certainly  the 
carboniferous  swamps  would  have  had  their  share  of  arctic 
denizens.  The  soft  mud  which  hardened  into  the  shales 
would  have  preserved  their  remains  -as  readily  as  those 
which  are  now  found  there.  Then,  as  the  wave  swept  on, 
and  after  thousands  of  years  returned,  and  again  the  polar 


fauna  and  flora  paused  on  their  northward  journey, 
all  the  centuries  of  that  slowly-returning  spring,  there  ought, 
by  every  reason,  to  have  been  left  in  the  mud  of  those 
swamps  another  layer  of  their  remains.  Yet  not  a  plant  nor 
an  animal  of  the  land  or  water,  proper  to  a  cold  climate,  was 
left  to  mark  their  once  abundance.  Remember,  the  polar 
fauna  and  flora  must  have  occupied  the  ground  as  long  as 
the  coal  plants,  and  note  the  overwhelming  abundance  of 
the  latter  and  the  total  absence  of  the  former.  The  thing 
seems  impossible. 

It  is  easy  to  explain,  as  Mr.  Croll  does,  the  absence  of  any 
great  amount  of  glacial  surface  marks,  on  the  supposition 
that  subsequent  glacial  or  atmospheric  action  has  obliterated 
them;  but  such  agencies  could  have  no  effect  upon  those 
other  records,  which  ought,  if  the  early  cold  periods  ever  ex- 
isted, to  have  been  securely  hidden  within  the  strata  them- 
selves. 

Again ;  the  condition  of  the  beds  of  coal  forbids  the  pos- 
sibility of  such  a  gradual  lowering  of  temperature.  If  Mr. 
CrolFs  theory  be  true,  the  heat  must  have  been  decidedly 
less  at  the  beginning  of  the  time  of  forming  a  coal  bed  and 
must  have  increased  until  the  middle  and  then  diminished 
until  coal  plant-life  again  became  impossible.  The  plants  at 
first  would  barely  live,  and  the  fossils  should  afford  only  a 
few  scant  species  of  the  more  hardy  kinds,  and  then  those 
less  hardy  with  increase  of  numbers  and  greater  luxuriance 
of  growth.  As  the  summers  grew  cooler  again,  these  middle 
species  would  have  died  out  and  a  flora,  such  as  marked  the 
beginning,  would  alone  remain.  But  the  fossils  give  no  such 
story  as  this.  On  the  contrary,  they  tell  of  a  "  warm,  moist, 
equable  climate"  and  give  not  a  sign  of  any  such  changes. 
The  only  argument  is  based  on  the  alternation  with  the 
coal  beds  of  layers  of  non-fossiliferous  materials,  some  of 
which  Mr.  Croll  thinks  are  due  to  glacial  action.  Granting 
that  he  is  correct  as  to  their  cause,  which  is  by  no 
means  certain,  they  are  consistent  with  the  absence  of  any 


2?* 

such  glacial  periods  as  he  requires,  if  we  admit  the  existence 
of  local  glaciers  during  these  early  periods,  a  supposition  no 
more  contradicted  by  the  admitted  warmth  of  those  times, 
than  a  like  cause  forbids  them  to-day  in  the  Himalayas  and 
Andes.  That  would  readily  account  for  the  limited  extent 
of  the  glacier  traces,  and  for  the  prevalence  in  the  same 
period  of  tropical  plants,  often  in  close  proximity.  The  in- 
stance cited  from  Dawsou,  is  remarkably  in  point,  and  gives 
exactly  the  conditions  we  should  expect  from  the  ice  coming 
from  higher  land  and  wasting  away  at  the  side  of  a  low  car- 
boniferous tract,  and  seems  inexplicable  on  any  other  theory. 
Moreover,  if  any  of  those  glaciers  reached  down  into  the 
seas  or  lakes  of  those  periods,  they  might  float  off  and  thus 
carry  to  a  distance  blocks  of  stone. 

To  this  it  may  be  said  that  no  sufficient  mountains  then 
existed,  and  I  am  aware  that  it  is  generally  thought  that  the 
surface  of  the  early  world  was  as  uniform  as  its  climate. 
But  what  man  can  believe  that  in  ages  when,  as  in  the  Alle- 
ghanies,  depressions  of  40,000  feet  were  made,  there  were  no 
corresponding  elevations  ?  The  simple  fact  that  these  im- 
mense depressions  were  filled  with  debris  brought  from  some- 
where, proves  the  existence  of  the  upheavals.'-' 

This  supposition,  if  sustained,  disposes  of  Mr.  CrolPs  as- 
sumption that  strata  without  fossils,  lying  between  fossilifer- 
ous  ones,  are  due  to  a  general  glacial  period. 

There  is  no  question  as  to  the  existence  of  a  warm  climate 
reaching  almost  to  the  poles,  but  all  the  evidence  which  he 
brings  to  prove  it,  has  no  special  bearing  on  his  theory,  since 
the  real  question  is  whether  the  admittedly  warm  period  was 
continuous,  or  whether  it  was  interrupted  by  periods  of  semi- 
telluric  cold,  and  the  latter  the  evidence  does  not  sustain. 

*The  average  thickness  of  the  stratified  rocks  is  probably  not  much  less  than  In 
Europe,  which  must  be  25,000  I'eet  and  more.  (See  Prof.  Dana's  Manual,  p.  145.) 
The  most  of  this  was  formed  before  the  Mesozoic.  It  is  difficult  to  see  where  all 
this  detritus  came  from  without  immense  upheavals.  Prof.  Ramsey  is  of  the 
opinion  that  in  pre-Miocene  times,  the  Alps  were  probably  higher  than  now.  He 
tlnds  thia  "  amply  demonstrated  by  the  enormous  thickness  of  fresh  water  and 
marine  deposits  of  the  Miocene  Age  now  spread  over  Switzerland,"  Pop.  Science 
Mo.,  Oct.  1875. 

PROG.  FO'K.  SOC.  NAT.  SCI. — VOL.  I. 


28 

I  have  spoken  of  the  Carboniferous  period  only,  but  the 
same  reasoning  applies  to  the  other  periods  down  to  the 
close  of  the  Tertiary. 

In  some  of  the  most  recent  deposits  long  after  the  Glacial 
Period,  there  are  found  mingled  together  the  bones  of  ani- 
mals, of  "which  some,  as  the  musk-ox  or  reindeer,  seem  to 
have  been  inhabitants  of  a  cold  country,  while  others,  as  the 
hyena  and  tiger,  appear  to  have  required  a  warm  region. 
This  is  exactly  what  we  should  expect  in  case  those  regions 
had  been  alternately  warm  and  cold.  The  presence,  there- 
fore, of  arctic  and  temperate,  or  sub-tropical  animals  in  the 
recent  deposits  is  proof  of  a  recent  alternation  of  climate 
from  some  cause,  while  their  absence  from  the  earlier  forma- 
tions is  evidence  that  no  such  alternations  then  occurred. 

The  fact  that  the  bones  are  mingled  is  to  me  incompre- 
hensible, if  the  animals  were  really  wide  apart  in  time  as  for 
instance  6,000  to  10,000  years.  For,  certainly,  if  a  layer  of 
arctic  animals  and  earth  was  made  and  then  left  alone  for 
thousands  of  years  until  astronomical  causes  could  have 
time  to  bring  the  needed  warm  climate,  the  stratum  would 
have  become  so  compacted  that  no  commingling  would  after- 
wards be  possible. 

In  regard  to  this  recent  or  Reindeer  Period,  I  note  two 
circumstances  which  seem  to  me  of  great  importance  in  their 
bearing  upon  Mr.  Croll's  theory. 

First,  It  lacks  the  telluric  character  to  be  expected  if  it 
was  due  to  changes  in  the  position  of  the  earth  and  the 
eccentricity  of  its  orbit.  A  cold  period  so  produced  should 
affect  the  whole  northern  hemisphere,  but  if  it  occurred  at  all 
on  this  continent  it  was  scarcely  arctic  in  character,  indeed,  it 
can  hardly  be  said  to  have  been  made  out  at  all. 

Second,  The  cold  came  on  "  suddenly  as  if  in  a  night,"  as 
Prof.  Dana  says.  Such  an  abrupt  change  could  in  no  way 
be  due  to  a  movement  in  a  cycle  requiring  22,000  yean-,  for 
for  its  completion. 

On  the  other  hand,  it  oilers  the  characteristics  of  a  climate 


made  colder  by  some  comparatively  sudden  surface  change 
affecting  the  elevation  of  the  land  or  the  direction  of  ocean 
currents. 

Such  a  period  so  produced  casts  light  upon  the  possibility 
of  early  local  glaciers. 

In  regard  to  these  earlier  periods,  I  am  glad  to  find  my 
conclusions  in  harmony  with  so  able  a  master  in  this  Science 
of  Geology  as  Sir  Charles  Lyell,  who  says  in  support  of  his 
belief  in  the  "  absence  of  re-current  Glacial  Epochs  in  the 
earlier  formations.  The  continuity  of  forms,  particularly  in 
the  class  of  reptiles  from  the  Carboniferous  to  the  Cretaceous, 
is  opposed  to  the  intercalations  of  glacial  epochs  correspond- 
ing in  importance  to  that  of  the  Post-Pliocene." 

Mr.  Geikie  devotes  a  very  large  part  of  his  book  to  show- 
ing that  in  Scotland  between  layers  of  the  till,  or  what  we 
here  call  hard-pan,  are  other  layers  indicating  a  wanner 
climate.  And  this,  I  think,  he  proves,  but  it  is  local  glaciers 
that  he  is  everywhere  dealing  with,  and  those  wholly  Post- 
Pliocene,  for  they  contained  remains  of  Bos  primigenius, 
Irish  Elk,  or  Deer,  Reindeer,  Mammoth,  &c.  The  direction  of 
the  scratches  of  the  marine  deposits  shows  local  action- 
"  What  positive  evidence  we  have  points  rather  to  the  exist- 
ence of  local  glaciers  in  the  higher  valley — to  'moderate  sum- 
mers and  severe  winters — during  such  inter-glacial  periods  as 
we  have  any  certain  records  of."  This  is  on  page  181  of  his 
Great  Ice  Age,  but  similar  evidence  is  found  almost  on  every 
page.  The  same  remarks  apply  to  the  glacial  traces  and 
warm  intervals  found  in  Switzerland.  The  explanation  is  in 
local  upheavals  and  subsequent  depressions,  examples  of 
which  abound  in  the  past. 

Mr.  Croll  attaches  great  importance  to  ocean  currents  as 
modifying  climate  and  devotes  several  chapters  to  showing 
that  they  are  due  to  the  winds. 

This  is  a  physical  question  of  great  interest,  but  uotjrital 
to  the  one  which  we  are  considering,  since  he  may  be  right 
as  to  the  cause  of  these  mighty  streams  and  yet  mistaken  as 


30 

the  theory  of  climatic  changes.  I  shall  therefore  dismiss 
it  without  further  remark. 

The  one  thing,  however,  which  Mr.  Croll  must  establish  or 
abandon  the  ground,  is  the  occurrence  of  many  real,  conti- 
nental, or  rather  semi-telluric,  glacial  periods,  alternating 
with  warm  ones.  Hence,  I  have  directed  your  attention  to 
iiri  examination  of  the  evidence  which  may  be  drawn  from 
the  presence  or  absence  of  the  fossils  which  wrould  character- 
ize such  climatic  vicissitudes. 

It  seems  to  me  that  the  Geological  records  fail  to  establish 
the  alternations  of  cold  with  the  acknowledged  warm  epochs 
But  if  the  evidence  had  proved  their  existence,  still  Mr. 
Croll's  theory  would  utterly  fail  to  account  for  the  remarka- 
ble fact  that  in  the  warm  intervals  always,  there  was  uni- 
formity of  plant  life  from  Spitsbergen  to  Florida.  If  telluric 
glaciers  really  existed  in  the  Carboniferous  and  other  early 
ages,  they  may  have  been  due  to  telluric  upheavals  of  a 
height  sufficient  to  make  the  cold,  but  not  to  affect  the  posi- 
tion of  the  earth's  axis.  We  find  no  evidence  of  that  until 
after  the  Pliocene. 

There  yet  remain  two  problems  whose  discussion  is  needed 
to  complete  what  I  desire  to  say  upon  this  subject. 

The  first  is  a  question  in  mechanics.  Certain  known  ef- 
fects are  given,  and  a  cause  is  suggested  as  accounting  for 
them.  Do  the  effects  correspond  to  the  assumed  cause? 
This  I  may  illustrate  by  a  homely  example. 

A  ship  is  seen  moving  against  the  wind  and  current.  To 
one  who  inquires  the  cause,  a  bystander  says,  "  It  is  a  man 
in  the  vessel  turning  a  crank  which  drives  a  propeller  screw." 
The  listener,  knowing  the  great  size  of  the  vessel,  and  the 
power  of  the  wind  and  current,  would  at  once  pronounce  the 
#ause  inadequate,  or  in  other  words,  the  known  effect  to  be 
too  large  for  the  cause  assigned.  On  the  other  hand  it  is 
easy  to  imagine  cases,  where  the  effect  should  not  be  large 
enough. 

This  is  the  kind  of  problem  which  we  liara  now  to  solve, 
.and  it  may  be  thus  .stated, 


The  moon,  on  the  supposition  that  its  orbit  was  once  in 
the  plane  of  the  earth's  equator,  and  that  they  both  were 
then  inclined  to  the  ecliptic  only  U  cleg.,  has  been  so  moved 
that  its  orbit  is  now  inclined  5  cleg.,  9  mm.  This  would  re- 
quire an  actual  uplifting  of  the  moon  of  at  least  3  deg.  39 
min.,  or  13,200  miles. 

Now  calling  the  earth's  radius  and  mass  each  1,  the 
distance  to  the  moon  will  be  GO  and  its  mass  about  1-90.  It 
is  easy  to  show  that  any  polar  force  on  the  earth  will,  by  the 
laws  of  resolution  of  forces,  lift  the  moon  from  the  ecliptic 
with  a  force  1-60  as  great  as  that  which  tends  to  draw  it  di- 
rectly towards  the  earth,  or  the  earth  towards  the  moon ; 
and  since  the  hitter's  mass  is  only  1-90  of  the  earth's,  it 
would  be  moved  90  times  as  lar:  or  combining  the  two 
ratios,  the  actual  movement  of  the  m_>on  will  be  90-GO,  or  11 
times,  that  of  the  earth.* 

This  force,  then,  would  move  the  earth  2-3  of  13,200  miles, 
which  is  8,800 ;  but,  being  applied  at  the  terrestrial  pole  as 
a  tangent,  it  tends  also  to  make  it  (the  pole)  rotate  towards 
the  ecliptic,  and  ought  to  cause  it  to  pass  through  22,000 
miles, — almost  a  circumference.  But,  in  fact,  the  pole,  in 
going  from  11°  to  231°,  travels  only  1,320  miles;  and  not  all 
of  this,  even,  is  due  to  the  moon,  for  there  is  the  effect  pro- 
duced by  the  sun,  of  which  I  have  said  nothing. 

The  resulting  motion  seems  greatly  less  than  it  ought  to 
be.  Is  it  really  so  ?  And  shall  we  be  obliged  to  discard  the 
supposed  cause  of  this  movement  and  seek  another  ?  If  not 
what  has  become  of  the  excess  of  force  ? 

If  on  exhaustive  examination,  it  shall  appear,  that  the  ef- 
fects are  in  fact  too  small  and  that  the  excess  cannot  be  ac- 
counted for,  then  we  are  on  the  wrong  track  and  must  begin 
anew. 

To  seek  to  answer,  therefore,  this  question  is  our  next 
business. 

*As  there  is  no  attempt  here  to  solve  these  questions  numerically,  I  have  used 
for  the  ratios  only  convenient  approximations, 


32 

Here  comes  in  an  interesting  and  curious  principle,  viz., 
the  persistence  or  fixity  of  the  plane  of  rotation.  A  body  re- 
volving on  an  axis  can  be  made  to  change  the  direction  of  its 
motion,  but  only  at  the  expense  of  force  employed  in  over- 
coming that  persistence.  We  see  this  principle  in  that  modi- 
fication of  the  Gyroscope,  called  the  Mechanical  Paradox. 
This  consists  of  a  disk  revolving  on  pivots  within  a  ring, 
having  on  the  line  of  prolongation  of  its  axis  on  one  side,  a 
bar  or  spur  with  a  smooth  notch  beneath,  to  receive  the  hard, 
smooth  point  of  an  upright  support.  If  now  the  disk  is 
made  to  rotate  rapidly,  and  the  bar  be  set  upon  the  sup- 
porting point,  the  whole  begins  to  revolve  slowly  around  the 
point  and  to  slowly  fall.  Gravity  acts  freely  upon  the  un- 
supported end,  and  yet  such  is  the  persistence  of  the  plane 
of  rotation,  that  it  falls  only  an  inch  or  two  in  many  seconds. 
Almost  the  entire  force  of  gravity  is  expended  in  moving  it, 
and  only  the  merest  fraction,  in  making  the  ring  actually  fall. 
If  its  descent  is  only  5  inches  in  10  seconds,  then  all  but 
1-3840  of  gravity  is  thus  consumed.  The  more  slowly,  how- 
ever, the  disk  rotates,  the  more  rapidly  it  falls,  and  the  less 
is  the  proportion  expended  in  moving  the  fixed  plane.  Now 
in  this  case,  the  earth  may  be  regarded  as  a  rotating  disk, 
and  the  lunar  attraction  upon  the  circumpolar  upheaval,  as 
the  attraction  of  gravitation  tending  to  pull  the  disk  down, 
and  the  effect  produced  is  the  amount  of  fall;  hence  the 
greater  part  of  the  force  should  be  expended  in  changing  the 
plane  cf  rotation,  and  only  a  small  proportion  in  actual 
movement  of  the  earth. 

As  the  attraction  of  the  terrestrial  polar  upheaval  had  no 
tendency  to  change  the  plane  of  the  moon's  rotation,  its 
whole  force  was  expended  in  lifting  the  moon,  so  to  speak, 
from  the  ecliptic.  Hence  if  the  hypothesis  under  consider- 
ation is  true,  the  actual  distance  of  the  moon  from  its  normal 
position,  ought  to  be  much  greater  than  that  through  which 
the  pole  of  the  earth  has  moved,  and  observation  shows  that 
such  is  the  case. 


33 

It  would  be  very  desirable  to  calculate  what  should  be 
upon  this  theory,  the  ratio  of  the  two  movements. 

This  is  a  problem  of  great  difficulty,  but  not,  I  think,  in- 
solvable.  For  the  present  we  must  rest  satisfied  with 
showing  that  the  actual  movement  of  the  moon  ought  to 
have  been  much  greater  than  that  of  the  earth,  a  result  that 
fully  agrees  with  the  statement  already  made,  that  the  moon 
has  moved  13,200  miles,  while  the  pole  of  our  earth  had 
traveled  only  1,320. 

The  other  problem  of  which  I  spoke  pertains  to  the  reason 
of  these  upheavals ;  what  caused  them  ? 

My  inability  to  answer  this  question,  would  not  effect  the 
fact  of  their  occurrence,  but  only  leave  me  in  the  presence  of 
a  great  physical  phenomenon  of  whose  cause  I  am  ignorant ; 
a  position  in  which  every  scientist  finds  himself  in  reference 
to  very  many  of  the  phenomena  about  him. 

To  explain  these  movements  there  must  be  found  a  force 
sufficient  to  elevate  simultaneously  the  circumpolar  regions 
of  both  hemispheres,  covering,  as  they  do,  many  millions  of 
square  miles,  a  force  able  to  do  this,  not  spasmodically,  but 
so  slowly  and  uniformly  as  to  produce  little  contortion  or  dis- 
placement of  the  strata.  Moreover,  a  true  solution  must 
account  for  the  fact  that  these  upheavals  were  not  permanent, 
and  that  after  a  time,  probably  a  very  long  time,  they  sank 
back  again. 

A  little  reflection  will  show  that  this  is  a  problem  of  great 
difficulty.  I  have  often  attempted  it,  and  have  as  often  been 
baffled ;  nor  am  I  now  prepared  to  assert  that  I  have  solved 
it.  I  can  only  say  that  in  certain  other  physical  phenomena, 
I  think  1  see  a  glimmer  of  light  that  may  lead  out  of  the 
darkness  which  at  present  surrounds  the  subject. 

It  will  be  necessary  to  go  back  to  a  period  when  the  globe 
was  a  ball  of  molten  lava — a  fluid  and  subject  to  the  laws  of 
fluids.  It  is  evident  that  in  such  a  compound  mass,  those 
substances  which  solidified  first  and  were  of  least  specific 
gravity  would  float  on  the  surface  as  slag  on  melted  iron.  It 


84 

is  well  known  that  the  present  crust  is  only  about  2-5  as 
heavy  as  the  interior  and  that  it  is  composed  of  the  most 
refractory  substances.  Hence,  for  a  time  at  least,  there  was 
a  floating  crust,  like  ice  on  a  pond.*  By  the  laws  of  motion 
any  such  floating  crust  tended  towards  the  equator,  and 
hence,  we  are  justified  in  concluding  that  the  crust  was  thick- 
est in  these  parts,  and  for  precisely  the  same  reason — thin- 
nest at  the  poles.  After  a  certain  thickness  of  crust,  probably 
some  hundreds  of  miles,  had  been  formed,  we  may  suppose 
the  supply  of  like  materials  exhausted,  and  the  globe  to 
have  gone  on  cooling  without  much  apparent  change  until, 
after  a  sufficient  tinio,  the  interior  approached  the  tempera- 
ture at  which  a  portion  of  it  began  to  grow  more  consistent 
and,  it  may  be,  to  reach  the  solid  condition  ;  a  supposition 
strongly  corroborated  by  certain  astronomical  observations  in 
reference  to  the  movements  of  the  moon,  which  appear  to 
indicate  that  the  interior  is  not  now  a  fluid. 

It  is  well  known  that  at  least  one  fluid  contracts  with  a 
decrease  of  temperature  to  a  certain  point,  and  then,  with 
further  decrease  actually  expands,  until  it  becomes  solid, 
after  which  it  again  shrinks  as  the  temperature  falls.  A  sim- 
ilar increase  in  bulk  is  said  to  occur  where  certain  metals 
assume  the  solid  form.  Plaster  of  Paris  expands  at  time  of 
*'  setting."  A  change  in  the  dimensions  of  some  bodies  takes 
place  when  an  electric  current  passes  around  them.  It  seems 
highly  probable  that  expansion  takes  place  when  melted 
substances  pass  into  a  crystaline  form.  The  force  put  forth 
at  such  times  is  immeasurable. 

Now  apply  this  to  the  earth.  In  the  process  of  cooling, 
its  interior  had  arrived,  we  will  suppose  about  the  close  of 
the  Tertiary,  at  a  temperature  when  like  water  at  40°,  it  be- 
gan to  expand  with  further  cooling.  This  expansion  pro- 
duced a  slow  and  equable,  and  practically  irresistible  pres- 
sure upon  the  surrounding  crust,  which  had  to  yield  at  the 

*  If  it  is  true  true  th'it  granite  shrinks  8  per  cent,  i a  solidifyingf.it  would  still 
be  much  lighter  than  the  average  l  lava  "  wuich  made  up  the  earth. 


85 

weakest  points,  and  these  were  the  polar  regions  because  the 
crust  was  there  thinnest  and  flattest.  Consequently  those 
parts  were  pushed  outward,  that  is  upwards,  to  an  extent 
limited  only  by  the  duration  of  the  force,  or  the  cohesive 
power  of  the  crust. 

The  only  other  thing  that  could  occur,  was  to  break 
through  the  crust,  but  when  the  great  extent  of  the  flattened 
portions  (50,000,000  square  miles  each)  is  considered,  it  will 
be  seen  that  flexure  would  be  much  easier  than  rupture. 
For,  if  the  crust  were  300  miles  thick,  its  flexibility 
would  be  represented  by  that  of  an  iron  bar  80  feet  long  and 
1  foot  square,  and  the  necessary  flexure  by  a  drooping  at  the 
centre  of  less  than  1  inch.  Such  a  bar  supported  at  each 
end  would  bend  by  its  own  weight  many  times  as  far. 

Nor  was  the  expansion  needed  to  raise  the  polar  regions  to 
the  surface  of  the  circumscribed  sphere  proportionately 
very  great,  being  only  4-1000  of  the  bulk  of  the  fluid  con- 
tents. Mercury  expands  1-10,000  for  every  degree  of  heat 
added ;  if  the  mass  in  its  cooling  obeyed  the  same  law,  it 
needed  only  to  lose  40°  of  heat,  a  very  small  amount  indeed 
in  reference  to  its  high  temperature. 

Such  an  expansion  would  give  the  kind  of  force  required. 
It  would  lift  the  crust  with  a  slow  and  equable  motion,  and 
hence  would  produce  little  disturbance  in  the  order  or  incli- 
nation of  the  strata.  The  surface  would  be  raised  in  lines 
so  long  that  their  flexure  would  be  imperceptible,  and  there 
would  be  required  only  a  slight  elongation  in  a  polarward 
direction.  Its  effects  would  reach  nearly  to  the  equator,  and 
its  pressure,  being  by  the  laws  of  hydrostatics  equal  in  all 
directions,  would  push  out  one  pole  with  the  same  force  and 
at  the  same  time  as  the  other. 

Although  such  a  movement  would  change  the  earth's  sur- 
face to  that  of  a  true  sphere,  yet  owing  to  the  centrifugal 
force,  the  practical  effect  would  be  the  same  as  raising  an 
immense  mountain  to  the  same  height,  or  more  accurately  a 
plateau  sloping  on  every  side  towards  the  equator.  Such  an 

PEOC.  PO'K.  SOC.  NAT.  SGI. — VOL.  I. 


36- 

elevation  would  produce  the  most  intense  cold.  As  it  gradu- 
ally rose,  the  water,  in  a  great  part  at  least,  flowed  toward 
the  equator  and  would  have  accumulated  there  but  for  a 
counteracting  force.  It  is  well  known  that  the  air  takes  up 
water  at  any  temperature,  as  long  as  its  capacity  is  not  satis- 
fied. That  which  rose  from  the  equatorial  seas,  passed 
towards  the  poles  and  there  deposited  its  moisture,  not 
as  rain,  but  as  ice  and  snow,  and  then  returned  for  a 
new  supply,  just  as  in  the  well  known  philosophical  toy 
called  the  Cryophorus,  the  water  is  transferred  from  the 
warm  to  the  cold  bulb  and  there  frozen,  until  all  is  exhausted. 
How  complete  the  transference  was,  depended  only  on  the 
duration  of  the  process  and  the  intensity  of  the  cold,  and  not 
as  has  been  said  upon  any  extraordinary  heat  to  produce  an 
unusual  amount  of  evaporation.* 

The  earth  having  become  nearly  or  quite  spherical  by  the 
internal  expansion,  the  waters  of  the  ocean  piled  as  ice  in 
circumpolar  regions,  gave  the  extra-spherical  masses  required, 
which,  by  the  help  of  solar  and  lunar  attraction,  produced 
the  increase  of  the  axial  inclination  of  the  earth  as  well  as 
the  change  in  the  position  of  the  moon's  orbit. 

The  cause  of  these  upheavals,  so  far  as  it  depended  upon 
the  internal  expansion  which  we  have  been  considering, 
reached  a  limit  as  soon  as  the  solidifying  process  was  com- 
pleted on  the  part  of  those  portions  of  the  fluid  contents  of 
the  earth  which  congeal  at  such  a  high  temperature.  After 
this,  farther  cooling  produced  contraction  as  in  other  solids, 
for  even  ice  shrinks  by  farther  increments  of  cold. 

A  reportf  on  casting  broaza  guns  made  to  the  Secretary  of 

*NOTK. — It  has  been  said  that  a  low  equatorial  temperature  would  not  give 
moisture  enough  to  form  the  Glaciers.  To  test  this,  I  filled  a  tin  vessel  with  salt 
and  snow  and  placed  it  out  of  doors  where  the  thermometer  stood  at  31°.  In  about 
twenty  minutes  the  sides  were  covered  with  Irozen  moisture  to  such  a  depth  that 
I  could  easily  scrape  it  off  in  little  pellets,  In  this  case  after  a  time,  the  process 
would  have  ceased  on  account  of  the  non-conducting  power  of  the  rime.  But 
if  it  had  heen  removed  the  process  would  have  continued  for  any  length 
of  time  I  chose  to  keep  it  up.  So  in  polar  regions.  The  frozen  moisture  was  at 
once  deposited  on  the  ground  and  there  remained  as  ice,  while  the  air  went  back 
fora  fresh  supply.  The  amount  and  rapidity  of  the  transference  depended  upon 
the  difference  between  the  polar  and  the  equatorial  temperature. 

t  "Reports  of  Experiments  on  the  strength  and  other  properties  of  Metals  for 
Cannon." 


37 

War,  1856,  gives  some  observations  which  are  interesting  in 
this  connection  (page  295.) 

In  casting  a  large  gun  the  mould  was  poured  even  full. 
At  first  the  surface  sank  down  II  inches  below  the  top. 
Soon  after,  it  presented  an  appearance  as  of  ebulition,  as  of 
gases  escaping  and  expelling  the  more  fluid  portions  of  tho 
alloy,  which  rose  and  overflowed  the  mould,  and  when  it  be- 
came solid  it  projected  considerably.  After  it  became  solid 
it  was  at  first  of  course  very  hot,  and  while  becoming  cold  it 
must  have  shrunk  as  any  other  metal.  Unfortunately  for 
our  purpose  no  account  is  given  of  the  last  shrinkage. 
Probably  it  was  the  same  as  in  case  of  any  other  piece  of 
bronze. 

In  this  instance  there  was  first  a  shrinkage,  then  an  ex- 
pansion, then  a  cessation  or  standing  still,  and  lastly  a 
second  shrinkage,  all  under  the  influence  of  a  falling  temper- 
ature. 

We  may  suppose  then  that  the  farther  cooling  of  which  I 
have  spoken,  went  on,  which  after  a  time  resulted  in  a 
shrinkage,  causing  the  weaker  portions  of  the  crust  to  fall  in. 
These  were  the  polar  regions  since  they  were  the  thinnest, 
and  the  equatorial  belt  was  pressed  outward  by  the 
centrifugal  force.  I  have  not  thought  it  necessary  to  con- 
sider the  effect  of  the  arch,  for  on  so  long  an  arc,  the  most 
perfect  homogeneity  and  regularity  would  be  necessary,  and 
these  would  be  destroyed  by  the  slightest  variation.  In 
short,  the  polar  regions  would  offer  the  least  resistance  to  a 
movement  in  either  direction. 

If  under  the  enormous  strain  generated  by  the  centrifugal 
foice  while  the  polar  diameter  was  elongated,  the  equatorial 
belt  at  last  yielded  so  much  as  to  be  lengthened  1-16  of  one 
per  cent.,  the  additional  space  thus  gained  would  take  up  the 
entire  amount  needed  to  change  the  sphere  to  its  present 
form. 

I  see  no  reason  why  similar  alternate  expansions  and 
contractions  might  not  have  occurred  at  various  epochs  in  the 


world's  history,  for  the  contents  of  the  earth  mast  be  com- 
pounded of  many  substances,  each  having  its  own  point  of 
congelation,  and  it  is  quite  possible  that  as  the  temperature 
fell,  the  time  of  reaching  each  one  of  these  may  have  been 
marked  by  some  such  movement,  either  of  expansion  or  con- 
traction. Possibly  this  action  on  a  limited  area  may  account 
for  some  of  the  local  movements  which  are  so  perplexing. 

Whatever  may  be  thought  of  this  as  the  explanation  of  a 
hitherto  unsolved  problem,  I  think  I  may  safely,  say,  it  is 
based  upon  facts  and  possibilities,  and  violates  no  law.  I 
offer  it  for  your  consideration. 

In  conclusion  I  will  briefly  sum  up  the  facts  stated  and 
the  deductions  which  I  have  drawn  from  them. 

The  earth's  axis  at  the  moment  of  separation  from  the 
lunar,  belt  was  inclined  not  more  than  1 1  deg,  and  is  now  in, 
clined  231  deg. ;  hence  at  some  time  an  increase  of  obliquity 
occurred 

Astronomy,  or  Celestial  Mechanics,  gives  no  indication  as 
to  the  time  of  this  increase.  It  tells  of  possible  conditions, 
arising  from  solar  and  lunar  attraction  upon  circumpolar  up- 
heavals, and  manifested  in  the  change  of  the  moon's  orbital 
inclination  from  1°  30/  to  5°  9',  but  gives  no  intimation  as  to 
the  epoch  at  which  the  movement  actually  occurred.  We 
turn  then  to  Geology,  and  this,  as  I  read  it,  is  the  story  ifc 
tells. 

At  the  dawn  of  life,  as  the  land  was  just  beginning  to  ap- 
pear, a  tropical  warmth  extended  to  the  poles.  This  was 
due,  in  part,  to  the  limited  extent  of  land  surface,  in  part,  to 
ocean  currents,  but,  in  a  much  greater  degree,  to  the 
presence  of  carbonic  acid,  and,  perhaps,  other  impurities  in 
the  atmosphere,  which,  while  freely  permitting  solar  heat  to 
reach  the  earth,  acted  as  a  barrier  to  its  escape. 

A  free  exchange  of  aerial  and  ocean  currents,  and,  perhaps, 
a  persistent  belt  of  equatorial  clouds,  equalized  the  tempera- 
ture of  what  are  now  torrid  and  arctic  regions,  and  aided  iu 
producing  uniformity  of  biological  development* 


As  the  ages  passed,  the  carbonic  acid,  by  various  chemical 
processes,  was  taken  from  the  air  and  stored  away  as  coal  or  as 
carbonates.  While  this  was  going  on  the  warm  covering  grew 
thinner,  and  more  heat  was  radiated  back  and  lost  in  space  I 
and,  although  uniformity  and  equability  of  climate  long  re- 
mained, yet  the  earth's  temperature  was  slowly  falling. 

The  flora  of  the  Miocene  was  one  demanding  days  ami 
nights  of  equal  (i.  e.,  not  polar,)  length,  yet  indicating  a 
climate  cooler  than,  for  instance,  in  the  Cretaceous.  In 
short,  the  thermal  lines  were  falling  towards  the  equator. 

The  earth's  surface  during  this  long  period  was  under- 
going great  changes.  There  were  vast  depressions  and  corre- 
sponding elevations,  rising  sometimes  into  mountains  perhaps 
higher  than  any  now  existing.  On  some  were  local  glaciers, 
forming  moraines  and  depositing  their  debris  in  the  warmer 
valleys. 

The  same  agencies  which,  at  later  periods,  obliterated 
other  mountains  may  have  worn  those  away ;  or,  like  de- 
pressing forces,  may  have  brought  them  down.  Some  such 
movements  were  probably  the  cause  of  the  limited,  earlier, 
glacier-like  traces,  found  in  various  places. 

But  all  along,  in  every  place  where  there  are  fossils  to  tell 
the  story  of  climatic  condition,  there  is  a  lack  of  proof  of  sea- 
sonal vicissitudes,  or  polar  nights  of  months'  duration.  This 
I  understand  to  be  the  evidence  of  plant-life  and  animal-life 
from  the  dawn  of  existence  to  near  the  close  of  the  Tertiary > 
and  from  it  I  conclude  that  thus  far  the  axis  of  our  earth 
was  still  nearly  perpendicular  to  the  ecliptic. 

How  long  the  Glacial  period  lasted  is  unknown,  but  at 
last  it  drew  towards  its  close,  and  plant-life  revived.  The 
geological  record  after  this  is  far  inferior  in  sharpness  of  defi- 
nition to  that  which  preceded  it,  but  as  soon  as  the  story  can 
be  read  with  certainty,  it  tells  of  zones  of  climate,  alter- 
nations of  seasons  and  long  polar  nights  and  days.  The  mo- 
notonous uniformity  of  the  past  is  gone  forever.  Admitting 
the  uniformity  of  law,  that  like  causes  produced  like  effects 


as  well  in  the  remote  past,  as  in  the  present,  I  see  no  way  to 
escape  the  conclusion  that  during  this  period  of  circumpolar 
elevations,  the  axis  of  "our  earth  attained  its  present  ob- 
liquity. 

However  difficult  it  may  be  to  believe  it,  or  even  to  con- 
ceive of  it,  the  fact  remains  that  in  some  way  the  earth  has 
attained  its  present  position,  and  nothing  is  gained  by  re- 
ferring the  movement  to  some  unknown  and  more  remote 
period  when  "somehow  it  got  tilted  to  one  side,"  and  we 
should  remember,  too,  that  no  more  power  was  needed  to 
change  its  inclination  after  it  had  existed  through  the  geo- 
logical ages,  than  before. 

I  have  elsewhere  (see  note  at  the  end  of  this  Essay)  shown 
that  this  great  event  could  not  have  been  due  to  magnetic 
forces,  as  some  have  thought,  nor  to  collision  with  meteors, 
as  lately  suggested,  nor  to  centrifugal  forces,  as  at  one  time 
asserted ;  and  that  while  it  might  have  been  due  to  a  mira- 
cle, yet  such  an  interference  is  highly  improbable,  because 
every  member  of  the  solar  system  has  its  axis  more  or  less 
inclined,  not  excepting  the  Sun,  where  nights  are  impossible, 
and  seasons,  the  supposed  object  of  such  a  miracle,  are 
inconceivable. 

Being  thus  compelled  to  seek  some  other  cause,  I  ex- 
amined into  the  effects  which  could  be  produced  by  the  at- 
traction of  the  Sun  and  Moon  on  circumpolar  upheavals,  and 
found  here  a  force  that  could  compel  the  Axis  to  become 
more  oblique.  I  then  went  over  the  records  of  plant  and  ani- 
mal life,  and  found  a  condition  and  distribution  that  seemed 
to  me  inexplicable  unless  the  axis  had  thus  far  retained  its 
perpendicularity.  I  found  this  period  ©f  uniformity  followed 
by  a  time  of  groat  cold  and  enormous  circumpolar  upheavals, 
and  after  the  cold  disappeared  the  uniformity  so  marked  be- 
fore, was  gone  forever.  I  concluded  then  that  in  the  interval 
was  the  epoch  of  this  great  event. 

As  far  as  I  can  sec,  the  only  objection  to  this  conclusion  is 
the  .greatness  of  the  upheavals  required.  I  submit,  however, 


41 

that  this  objection  is  not  fatal,  since  absolutely  nothing  is 
known  of  the  extent  of  these  movements,  nor  of  the  nature 
or  limits  of  the  force  producing  them. 

Besides,  the  greatness  of  which  we  speak  is  only  relative 
to  man.  Compared  with  the  globe  itself  they  sink  into  insig- 
nificance, the  height  being  scarcely  one-third  of  one  per  cent, 
of  the  radius,  or  one-fiftieth  of  an  inch  on  a  thirteen-inch 
globe,  an  amount  which  no  unaided  eye  could  perceive. 

The  objection  which  arises  from  the  inequality  between  the 
movements  of  the  moon  and  of  the  pole,  is  not  only  accounted 
for,  but  shown  to  be  necessary  to  the  truth  of  the  theory. 

Omitting  all  reference  to  the  supposed  cause  of  the  polar 
upheavals,  since  its  truth  or  falsity  does  not  effect  the  argu- 
ment, the  condition  of  our  system,  the  laws  of  motion  and  the 
record  of  Geology  are  such  that  I  feel  compelled  to  believe 
that  we  have  arrived  at  two  great  and  important  facts  in  the 
history  of  our  world;  1st,  that  from  the  moment  of  separation 
from  the  lunar  belt  until  well  towards  the  close  of  the  Tertiary, 
its  axis  was  nearly  perpendicular,  its  obliquity  not  exceeding 
11° ;  and,  2nd,  that  the  increase  to  23 \°  occurred  during  that 
period  of  cold  which  followed  the  Pliocene  and  which  ia 
usually  known  as  the  Glacial  Period. 

NOTE  1.  In  the  Essay  upon  Cosmology  which  forms  Part  III  of  the  Miracle  of 
To-day,  I  have  treated  quite  fully  of  several  points  to  which  I  have  only  alluded  in 
this  article.  The  one  is  in  some  respects  the  complement  of  theother. 

NOTE  2.  The  early  uniformity  ef  climate  as  indicated  by  the  fossils  is  admitted 
by  all  modern  Geologists.  For  the  convenience  of  those  who  have  not  looked  into 
the  matter  I  add  a  tew  references  to  Prof.  Dana's  Manual  of  Geology,  1874,  "  No 
Zones  of  Climate,"  see  p.  181,  209.  253/289,  Xi2,  452,  480. 

NOTE  3.  My  attention  nas  been  called  to  the  allefffd  discovery  in  Siberia  of  vines 
bearing  fine  grapes  within  the  Arctic  circle,  and  the  question  has  been  asked,  how 
such  a  fact  affects  my  theory.  I  reply  that  it  comes  under  the  case  already  con- 
sidered, of  species  of  a  wide  range,  on  page  14.  If  it  had  been  shown  that  these 
vines  had  been  kept  during  the  long  Arctic  winter  in  a  warm,  moist,  equable  at- 
mosphere, as  during  the  Carboniferous  Period,  and  had  continued  to  do  well  in  the 
Arctic  summer,  the  case  would  have  been  analogous  to  that  of  the  early  flora, 
but  as  there  are  no  such  conditions  now  in  polar  regions,  the  cases  are  entirely 
different. 


14  DAY  USE 

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General  Library 

University  of  California 

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Pamphlet 

Binder 
Gaylord  Bros. 

Makers 

Syracuse,  N.  Y. 
PM.JAI  21,1308 


